1. Field of the Invention
This invention relates to a two-beam spectrophotometric method and apparatus, in which a beam of light coming from a light source and dispersed at a monochromator is divided by a beam splitter into a first measuring beam which is passed along the optical axis through a measuring cell to a measuring detector, and a second reference beam which is passed to a reference detector.
2. Description of the Prior Art
Two-beam spectrophotometers (also called spectrometers) are known in the art. To allow spectral analysis with high signal resolution, the base line of such apparatus should be as flat as possible. This means that the spectral intensity distribution of the measuring and reference beams should have a substantially identical curve, but is is well known that this is not the case with the prior art devices and methods.
In certain wavelength ranges considerable intensity fluctuations occur and require the use of complex and expensive electronic equipment for correction. The fluctuations in spectral intensity associated with the prior art devices are largely attributed to polarization effects of the grating in the monochromator and the beam splitter.